USA > Massachusetts > Norfolk County > Norwood > Norwood annual report 1908-1911 > Part 29
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Rock was encountered in nearly all the streets and consist- ed of a hard, brittle stone, easily drilled. This stone responded well to explosives and was usually broken into very small pieces.
On account of the careful work of the contractors, very lit- tle damage to abutting property was caused by blasting.
It is a satisfaction to be able to report that the work has been done without accidents to any of the employees.
CHANGES IN SIZE AND GRADES OF SEWERS.
The following changes were made in the size of the street
40
sewers as indicated by the plan submitted by Mr. Coffin in 1901 .
Dean street, cast iron pipe increased from 10 to 12 inches.
Dean street sewer increased from S to 10 inches.
Washington street from Dean street to near Douglas ave- nue, S to ro inches.
East Hoyle street from Broadway to Washington street, Io to 12 inches.
Broadway from E. Hoyle to Guild street, subway, 10 to 12 inches.
Guild street subway, 10 to 12 inches.
Lenox street from Guild street subway to Plimpton avenue, Io to 12 inches.
Washington street from East Hoyle to Winter street, 10 to 12 inches.
Washington street from Day street to Cottage street, 10 to 12 inches.
Market street from Washington to Nahatan street, 10 to I 2 inches.
Nahatan street from Maple street to near Prospect street, S to 10 inches.
Field line from Plimpton street to near Clark street, S to Io inches.
Williams street from Clark street to Lenox street, 6 to S inches.
After making a careful survey of Washington street, from Railroad avenue to Philbrick street, it was found that by lower- ing the sewer about two feet it would be possible to extend it to Philbrick street, also to take Granite and Warren streets into the gravity system, instead of the pumping system as originally planned. Thus provision was made for the sewerage of 17 houses already constructed and any that may be built upon these streets in the future. The total cost of making the necessary changes in Washington street was $1150.
The depth of the sewer in Washington street from Market .street to Day street was also increased in order to accommodate
41
any deep cellars that may be constructed in the future.
CAPACITY OF MAIN LINES.
The 15-inch intercepting sewer through Nahatan and Lenox streets has a capacity of 2000 gallons per minute, or 2,880,000 gallons in 24 hours. This sewer receives the flow from practi- cally all of the gravity system lying north of Winter street, and west of the railroad. Considering the small amount of leakage, this would provide for a maximum flow of sewage from about 14,500 people. The 15-inch intercepting sewer through Plimpton avenue, and the right of way to Hillside avenue, and the 20-inch line from Hillside avenue to the upper end of the cast iron siphon have a capacity ot 2800 gallons per minute, or 4,032,000 gallons in 24 hours, or sufficient to discharge the maximum flow of sewage from a population of about 21,000 people. The siphon has a capacity of a little over 2,000,000 gallons in 24 hours. Should it become necessary to provide a greater capacity it can be done by allowing the siphon to work under an additional head sufficient to discharge 2,740,000 gal- lons in 24 hours, an amount equal to the maximum flow from a population of 14,000 people.
A 24-inch pipe is laid beginning at the lower end of the siphon and continuing for a distance of 1050 feet through the land taken from Willard Dean ; at this point the size is reduced to 15 inch and continues for about 1800 feet to the filter beds.
The capacity of the 24-inch line is 3500 gallons per minute, or 5,000,000 per day. The capacity of the 15-inch line from the 24 inch to the filter beds is 1300 gallons per minute, or 1,872,000 gallons per day.
Note : The capacity of the 24-inch pipe line is such that when it becomes necessary to provide more than 12 acres of beds, which area is available at the present location, the upper portion of the land bought from Nancy Page, and the land be- longing to Willard Dean lying between the Page property and the Neponset river, can be used if then available. The 15-
42
inch pipe has sufficient capacity to accommodate the quantity of: sewage, which can be filtered on 12 acres of beds at the present location.
In making the above statements as to the number of people for which the sewers will provide, I have assumed a leakage of 100,000 gallons per day (over eight times the measured amount at a time before any house connections were made), and that the average water consumption per capita per day would even- tually be 100 gallons, 75 per cent. of which will reach the- sewers, and that the maximum rate of flow will be 2 1-2 times. the average. This is the basis of calculation adopted by Mr. Coffin in preparing his preliminary report, exclusive of the- ground water assumption.
The basis of the foregoing statement appears to be very liberal. The present consumption of water is less than 60 gal- lons per capita per day, or 60 per cent. of the amount allowed for in this computation. It is also probable that the maximum rate- of flow will not materially exceed 150 per cent. of the water consumption, which would be at the rate of 150 gallons per- capita, instead of 187 1-2 gallons, as used in the foregoing com- putation, assuming an average comsumption of 100 gallons. It is therefore apparent that if the class of workmanship which has been secured in the construction of the sewers thus far built, .. is secured in the construction of the house drains and future ex- tentions of the sewerage system, the present trunk line and. siphon will provide for a very much larger population than indicated by this computation.
The extreme importance of excluding ground water from. the sewer system is emphasized by the fact that a leakage of 40,000 gallons per mile per day, which amount is not un -. commonly found to exist, would equal in rate of flow the maxi -- mum rate from 1700 people. This computation is based on the. S miles of sewers already constructed. To make reasonable- provisions for the sewerage of the entire town, about 20 miles. of sewers, including those already constructed, will be required,
43
and a leakage of 40,000 gallons per mile for the entire system would be equal to the maximum rate of flow from over 4000 people. It is also important to bear in mind that such an amount of leakage (Soo,000 gallons per day) would require considerable additional filtration area.
CAST IRON SIPHON.
The siphon is of 16 inch cast iron pipe, and runs from a point about 400 feet south of Hillside avenue, through the right of way to Willow street, thence through Willow street to Pleas- ant street, and in Pleasant street to the junction of the 24 inch field line leading to the filter beds, the total length being 3,876 feet. The pipe is laid from four and one-half to five feet below the surface and the joints are caulked with lead in the ordinary manner. The outlet or low end of the siphon discharges into a brick manhole at the head of the 24 inch line. The lower end of the siphon is 4.7 feet lower than the beginning or upper end, the hydraulic grade being 1.22 feet in 1,000. The lowest point in the siphon is when it crosses the Neponset river near Pleas- ant street. At this point the invert is 14.3 feet lower than the outlet. The siphon is laid on such a grade that it will drain from each end back to the river. A blow-off was placed at this point, also a cast iron hatch box or entrance chamber, thus pro- viding access to the siphon should it become necessary.
In constructing the inverted siphon a radical departure was made from the preliminary plans submitted by Mr. Coffin. The original design required the construction of a line about 3,400 feet in length wholly in private way, a portion of which was supported by piers. By adopting the siphon it was possi- ble to lay this part of the trunk sewer almost entirely in the highways, thus avoiding the expense of right of way, and the objectionable features of having a public sewer on private land. In addition to this advantage there was a saving in the cost of construction of about $3,500. While it is possible that eventu- ally the siphon will prove inadequate for the quantity of sewage
44
to be conveyed to the filter beds, it is believed that no increase of capacity above that which can be obtained by allowing the siphon to work under an additional head, will be necessary for years to come.
SEWER PIPE.
The sewers are all of vitrified pipe of the type known as deep and wide socket, the underdrains being of Standard vitri- fied pipe. All sizes of pipe 15 inches or more in diameter are extra heavy.
Branches are laid at proper points to connect all present and prospective houses upon the streets. These branches have five inch openings, it being proposed to lay the particular sewers of five inch pipe.
MANHOLES.
Brick manholes with iron covers are placed at every junc- tion of one sewer with another, and at all points where there is a change in the line or grade of the sewer, and on straight lines approximately 500 feet apart. The sewers are laid on straight lines between the manholes, and all curves or bends are made in the manholes, thus giving perfect control of the sewers for in- spection, cleaning and the removal of obstructions. By hand mirrors light can be thrown into the sewers and obstructions lo- cated. Jointed rods can be run through from manhole to man- hole and any obstruction removed.
This control and access to the sewers is essential, for, while obstructions are of infrequent occurence in a properly built and operated system, there is always the possibility of a stoppage.
FLUSHING MANHOLES.
Flushing is provided for by flushing manholes at the head of all lateral sewers. There is a flap gate placed on the outlet into the sewer from the manhole which can be held open by a chain fastened upon a hook in the manhole near the top. These manholes should be connected with the water main by a pipe about one inch in diameter. A valve should be placed on the
INTERIOR OF DOSING TANK .- ALL CONCRETE CONSTRUCTION.
---
45
end of the pipe inside the manhole. When it becomes necessary to flush the sewer the chain holding the flap gate open is releas- ed allowing the gate to shut. The valve on the water pipe is then opened and the manhole filled with water. When full the flap gate is opened allowing the water to rush into the sewer.
I advise that all of the flushing manholes be connected with the water mains as soon as possible in order that the sewers can be flushed without using the hydrants.
VENTILATION.
Ventilation of the system is provided by perforated covers on the manholes and by the omission of running traps on all house connections, thus leaving a free opening from the sewer through each such house connection and soil pipe to a point above the roof.
HOUSE SERVICES.
The connections from the street sewers to the houses will be five inches in diameter. Great care should be taken in the construction of the house services, and the joints made as nearly water tight as possible.
I should recommend that sulpliur joints be used in connec- tion with this work, and that in trenches where the material ex- cavated is unsuitable for bedding, the sewer pipe be laid in sand or gravel hauled from other locations. The services should be laid true to line and grade and at points where necessary to de- flect from a straight line a small manhole should be built.
SEWAGE DISPOSAL PLANT.
During the summer of 1907 a careful study was made of the lands lying south of and adjacent to the Neponset river and east of Pleasant street. Various portions of this land were sur- veyed and examined, and nearly 100 test pits were dug to deter- mine the character of the material underlying the top soil. Samples of the material from the pits were taken and subjected to mechanical analysis. It was found that a portion of the tract
46
of land belonging to the Page, Bird and Kingsbury estates was topographically favorable for the construction of filter beds and that the sand lying below the soil and sub-soil of this portion was excellent for the purposes of filtration.
The plant as constructed consists of a settling basin, dosing tank and about 6 1-2 acres of filterbeds.
The out-fall sewer extends from Pleasant street, through a right of way (taken by the town) to the disposal area. For a distance of 1050 feet from Pleasant street the sewer is laid in trench and is 24 inches in diameter. From the lower end of this portion of the out-fall sewer the pipe is 15 inches in diam- eter, and is laid in embankment. Because of the slight fall be- tween the end of the trunk sewer on Pleasant street and the water surface of the Neponset river the lower portion of the out- fall is laid at such an elevation that the water will stand in it from the settling basin to the upper end of the 15 inch pipe, a distance of about 1850 feet. It may be wise when cleaning the settling basin to temporarily close the lower end of the out-fall sewer, thus allowing the sewage to back up into the 24 inch pipe, so that when the settling basin is filled, the lower end of the out-fall may be flushed out. Several manholes have been provided in the 15 inch line, so that it will be possible to make an examination to ascertain if there is any material accumulation of sludge in the pipe. The fall in the 15 inch line is 3 feet, which insures a velocity, when running full or half full, of over 25 feet per second, which will be ample for flushing purposes.
GATE CHAMBER.
The out-fall sewer discharges into a gate chamber 16 feet long by 4 feet wide and 8 feet deep. This chamber is adjacent to and runs across the end of the settling basin. The sewage will pass from the gate chamber into the settling basin through three 10 inch sluice gates, which arrangement will provide suita- ble distribution of the sewage as it enters the basin. The in- verts of the 10 inch gates are two feet below the normal eleva-
.
47
tion of the surface of the water in the settling tank. A 10 inch by-pass sewer runs from the end of the gate chamber to the main distributing pipes leading to the filters. When it is neces- sary to remove the sludge from the settling basin, the gates through which the sewage ordinarily passes to the basin will be ·closed and the gate controlling the by-pass sewer will be opened, thus providing for the discharge of the sludge in the out-fall sewer through the by-pass directly onto the filter beds.
SETTLING BASIN AND DOSING TANK.
The sewage leaving the gate chamber will pass through a settling basin and then into a tank, through which it will be dis- charged at intervals upon the filters.
The first compartment of the combined tank constitutes the settling basin. It is 35.9 feet long, 28 feet wide and 9 feet deep, capacity being 67,000 gallons. The tanks are separated by a concrete wall, over which the sewage flows from the settling basin into the dosing tank.
The tanks are of concrete construction throughout. They are covered by a common roof of eliptical groined arch con- struction, 6 inches thick at the crown. The side walls are 2 feet thick and have a batter I-10 feet per foot in depth on the outside. The inside walls are vertical, the piers supporting the roof are 2 feet square, the span of the arches is 13 feet, and the rise 2 feet and 9 inches. The bottom of the tank is 6 inches in thickness.
A scum board is provided extending entirely across the set- tling basin, and is supported by means of brackets from the par- tition wall. This board is made of hard pine stock, one inch in thickness by 15 inches in width. The brackets supporting the board are adjustable, so that it may be raised or lowered, and drawn to or extended from the wall. As adjusted at present, it extends about 12 inches below and 3 inches above the surface of the sewage, is about 15 inches from the partition wall, and is in a vertical position.
48
The floor of the tank slopes 6 inches in both directions to- ward a 10 inch gate which controlls a drain provided for the removal of the sludge from the tank. The sewage will flow from the settling basin in a thin stream over the partition wall into the dosing tank. This feature, together with the method of admitting the sewage, will provide a nearly uniform distribution of flow through the settling basin, which should insure a satis- factory precipitation of the suspended matters.
It will be found that decomposition will become active in from four to eight weeks after the cleaning of the tank, depend- ing, in part, upon the season of the year. Frequent observation should be made to determine the extent of this decomposition, and when the bacterial action becomes rapid the flow should be shut off, and the contents of the tank flushed onto the sludge bed. Then the sewage admitted to the filter beds will be at all times comparatively fresh.
The dosing tank is 94.9 feet long, 28 feet wide and will contain 6 feet in depth of sewage. The capacity of this tank as governed by the siphon is approximately 110,000 gallons. The dosing appliances will provide for the rapid dosing of the filter beds, so that the maximum amount of time may be available for the filtration of the sewage and the subsequent aeration of the filters. While this is a feature which has not been universally adopted, it is believed that it will materially aid in maintaining the filters in an efficient condition. The rapid application of the sewage will assist in melting snow and ice which at times will be found on the surface of the beds, and it will also assist in the distribution of the sewage over the surface of the beds. It has been found that the entire contents of the tank are ordi- narily discharged in a period of approximately thirty minutes.
The sewage flows from the dosing tanks into the siphon chamber through a 24 inch sluice gate. There is also provided a 12 inch sluice gate by means of which the water may be drained from the dosing tank to the main distribution pipes. without passing through the siphon.
CONSTRUCTION OF UNDER-DRAINS IN FILTER BEDS.
49
SIPHONS.
The siphon chamber is 10 feet wide by 11 feet long, and is covered by a brick building. In the chamber are two 16 inch Miller automatic alternating siphons. The sewage enters the siphom chamber through the 24 inch pipe connecting with the dosing tank and is discharged through one or the other of the siphons alternately into one or the other of the two 20 inch main distributing pipes leading to the filters.
FILTER BEDS.
Six filter beds have been constructed, five of them being each 190 feet wide by 250 feet long. They have a combined. area of 5.45 acres. The sixth filter is 208 feet wide and 250- feet long, and has an area of 1.12 acres. The combined area' of all six filters amounts to 6.67 acres.
The character of the material is comparatively uniform throughout the beds, and is well adapted to the purification of sewage. The result of mechanical analysis of 12 samples of sand, so taken as to fairly represent all of the material, gave the following results :
No. 1, coefficient of uniformity, 14.19, effective size 0.31 mm.
2,
5.48,
" 0.31 ".
3,
14.1.7,
0.36
4,
5,
66
14.55,
66 0.57 66.
6,
66
17.SS,
66
0.52
7,
2.24,
66
0.21
66
8,
66
2.94,
6.85,
66
0.35
66
9,
IO,
3.45,
0.22
66
II,
66
2.46,
0.24
12,
7.34,
66
0.30
From these analyses and a number of others not included inve this table, it appears that the sand varies from 0.22 mm. to 0.57 mm. in effective size, the average size being 0.35 mm. The ma-
4
-
66.
10.55,
0.54
0.31
50
terial in certain parts of the beds is somewhat variable in size, although for the most part it is reasonably uniform. The co- efficient of uniformity varies from 2.24 to 17.88. The mini- mum depth of sand is approximately 3 1-2 feet. The maximum depth being approximately 5 feet.
DISTRIBUTION SYSTEM.
The arrangement of the filters is such that three are located on the easterly side and three on the westerly side of the main embankment, in which embankment are laid two distributing pipes. These pipes are each 20 inches in diameter and con- nected as already described, each siphon controlling one line of pipe. A manhole is provided at a point opposite the centre of each pair of beds. These manholes each contain two 12 inch shear gates controlling the pipes through which the sewage is discharged onto the respective filters. The sewage is admitted from the main distributors through the 12 inch lateral pipes to the surface distributors. One of these surface distributors is laid through the centre of each bed and extends from the main embankment, a distance of 200 feet, across the filter. They consist of concrete slabs six inches in thickness, laid in sections seven feet long, to prevent random cracks, and to which wooden sides are attached by means of iron rods turned up at the sides. Openings are placed in both sides of the distributors, 45 feet apart, and are provided with adjustable gates, by means of which the flow through the openings may be regulated, thus providing means for securing a uniform distribution of sewage over the surface of the beds, or providing for the application of a greater quantity of sewage to one side of the bed, should occa- sion require it.
UNDERDRAINS.
The effluent from the filters is discharged into the Neponset river, to which a main drain 20 inches in diameter has been laid. This drain is approximately 1100 feet in length and has been laid at a flat grade, as have also the various underdrains.
527.7'
$41.4
₦ 77'17 W
" Cast Iron Siphon
Willard
Dean
1
N Z
Area = 18 279 Acres from
Mary E. Woods
192.5'
816.5"
--
Mary E. Woods
NORWOOD SEWERAGE SYSTEM PLAN OF LAND TAKEN FOR SEWAGE DISPOSAL PURPOSES
Scale of feet
200
Lewis D Thorpe, Girl and Hydrovla Enquirer, Boston, TeLa.
N 14* 17' E
pipe
Embankmon
Vitrified
Fipe
9 72" 33' E
1423.10
Y 73' 09' W
240. 45
24* Vitrified
Pipe
-- 1
14 C
5 72 20 5
1099 75
John
Fiske
Willard
Dean
William
Liversidge
C 5 37 42C 15295
$ 71" 3B' [
392.4
$ 72º E
470.7
John Fiske
368 34 ₩ 133 %
₦ 75*39 ₩
927.9
Boundy
Underdrain
Total effective area of 6 filter beds = 6.63 Acres Area of Sludge bed
Vitrified
₦ 74'18'W
1092.3
laura
SI3' SAW
Heirs of Francis W.
Bir
U. D
397;
Heirs of Francis W. Bird
Maolso
Dosing Tan m
Heirs of Francis W. Bird
Outlet
Sludge Bed
Area . 36.681 Acres from Nancy M. Page
NEPONSET
RIVER
3 70 16 E 201+
PLEASANT
Heirs of Francis W., Bird
Jennie Fosberg
₦ 72° Ż0 W
829.4
7 9°427
Area = 11.820 Acres from
46a. R.
₦ 76, 06 ₩
347.8
3.22.75 312.99 2
44.5'
SL
407.9
5* 42'
Manhole
Manhole
Monhole
EL. 70.75
El. G9.75
16 .0*
to
Overflow ELGS.1
Flow Line?
Spring
Liney =
EL. 6475
Jeum
poard
Settling
Tank
24 Sluice Gate
Dosing
Tank
Surface
Natural
1 58.67
E1. 55.5
E1.55.75
G' Flap Gate
D
6' automatic Siphons
Section on line A- B
Embankment
Embankment
Surface
1917
20 pipes to
20 . 10 Y
filters -
is bend
1
Siphon Chamber
Dosing
A
10 * Sluice Gate
5 pipe
" 10am-
6- grave !!
10am2
gravel-
Partition
L/10' Sluice Gate
-
Sluice Cate
Pipe to Sludge Bed
Plan on spring line
Extra shingles
planed spruce boards
I layer sheathing paper
2x 10'plat
pine sheathing.
2" Spruce
plank
I
e' I beams
Section on line G - H
Section on ling I - J
Inverted plan on spring, line
54 2
Bed
75
Sludge
NORWOOD
SEWERAGE SYSTEM DRAWINGS OF
SETTLING AND DOSING TANKS
Scale of feat
0
10
Len .; D Thorpe Civil and Hydraulic Engineer Boston, Mass
a" I beam 13"0" long
Door
-F
Scale of feet
Plan
DETAILS OF HOUSE FOR SIPHON CHAMBER
Slope 14 to 1
C - D
Settling
Tank
Line
Wall
Section on line E -F
Embankment
Embankment
Natural ----
10" Pipe to Sludge Bed
Slope I> tol
- Natural_ _ Surface
Slope it to1
Filter
Filter
3"loam-
screened
Ordvel
earth
rBatter I to lo
ET 6185
lope
Slope 14 to
10" Bypass
sluice gate !
Tank
Section on line
Spring
6
.
35'9"
13467
long
18 - 9
CONSTRUCTION OF CARRIER ON FILTER BED.
D
FILTER
Scale
DRAWINGS OF
BEDS
SEWERAGE SYSTEM
Section of Distributing Chamber
Pipe
O
-4 0-
Stop plant
20"
Curry
Plan of Distributing Chamber
12
SStops
Vitrified
-
-
-
- -
56.5
f's to 6 Reducer 6 -
- Under drain EI SZ
-250
250
8 underdrain
-
-
A
Section
8
__ _ underdrain
£ O te & Reducer
- underdrain - --
31
EI
6.5
(8 to Reducer __ __ _ Underdrain
-
- EL52
4- 8_ underdrain.
Distributer
47!
O
56.51
Siopel
ro to @ Reduce :-
. Underdrain
EI 52
C
LEI 52
8 underdrain
250
250 -
8 Underdrain
-
58 to
Reducer -
tal
- underdrain -
9.
20-1
8 underdrain
I
C8 +. . Reduser -
10
underdrain -
Underdrains
FEL. 52
8
Underdrain
petos Reducer
Underdrown _ - -
£1_52
-
| 56.5
ce to G Reducer -
-
-
...
Distributer
Distributer
25-
8 underdrain
-
-
underdrain
EI 52 -
250
Et 50-
underdrain
8 to @ Reducer -
underdrain -
EI 52
3
10
Slope 1x ito
20" Underdrain Outlet
Siphon Chamber
Tank
Settling ! Tank v
===== 3
15" Outfall Sewer
to" P.p.
10
Underdrains
EI 54 25
Bed.
Sludge
El.| 54.25
obe
Centre
B
EI
56 5
EI 565
IS" underdrain
-8
underdrain
8 10 G Reducer
underdrain
Section on line C-D
2:19 - plank
Distributer
of Underdrain
Cross Section
Longitudinal Section of Underdrain
20
8
underdrain
-
-
underdrain
MH
Et 50.25
EL.
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